Actually Jordan, that's not quite right in this engine, if it was a single cylinder engine, then you're right. But with 4 pistons, each 180 degrees apart, theoreticly(sp) each piston will fill and/or displace the movement of its' opposite. I wish someone with a real fresh engine could put a gage in the oil filler hole and see just how much cranckcase pressure, if any, is generated by an engine at idle. That would be a great benchmark to see if, in fact the rings or valve guides are worn sufficiently to cause problems. Like blow oil out the sealing surfaces of the various gaskets. All that being said, with the engine at idle and the PCV system working, with max vacuum at idle and the small orifice in the intake manifold, would there be any pressure in the crankcase at all? I don't know, but it appears the pic that opeldean has, shows an excessive amount of pressure at idle. JMTCW

I've often wondered about this myself. I've rebuilt my engine 2 times over the 20 years I have owned it, and it has always been the same. I have no way of gauging it, but this engine has always seemed to have more of this crankcase pressure than any other non Opel engine I have ever owned.
BD

I have a fresh, less than 500 miles, rebuild 2.0L CIH from OGTS and it will lift a paper towel at idle like in OPELDEAN's picture. Prior to installing the 2.0L I went to add oil to my 1.9L while at idle, something I've done countless times with other engines, and it sprayed the fresh oil all over the place. My first thought was bad rings causing excessive crankcase pressure or worn valve guides so I yanked out the 1.9L and installed the 2.0L. Well low and behold the 2.0L does the same thing. Now that got me thinking, so I did a compression test and a leak down test on both engines and they are both within specs, of course the 2.0L is on the high side and the 1.9L is on the low side. Neither engine pushes oil out the PCV circuit. There seems to be a lot of air flow out of both engines at the filler cap but not much pressure. My car is all torn apart right now for painting but I'll rig up a pressure gage to the oil filler cap and check the PSI at idle and throughout the RPM range. Give me about a week and I'll post the results.

My fairly new engine (less than 2500 miles) also will blow the paper towel upwards and due to that I posted to this site awhile back about something I saw in a Blitz......but never got a response. Below is what i wrote.....any ideas on this?

*****I was just reading an Internet Tech Tip in an old Blitz (6/2000) about crankcase vacuum. In it there is a description of a hose teeing into the brake booster hose and leading to the valve cover, with an adjustable valve plumbed in. When the small line from the valve cover is plugged this creates a vacuum in the crankcase. The valve is adjusted until a vacuum at the oil filler hole is detected. This vacuum helps to reduce oil consumption.

Is this something we should consider doing on our cars. I have noticed on my 77 Datsun Z that there is a vacuum at the oil filler hole. It has a bazillion miles on the engine and doesn't leak any.... but does burn a little. Any ideas on this appreciated.******

Me too

I experienced the same thing and found it a bit troubling. Compression was 45 psi on #2 cylinder. Teardown showed lapped rings. I figured it was blow-by. I'm rebuilding the engine now and look forward to seeing if it still is so "windy" after rebuild.

Air Pressure at Oil Fill Hole

I finally had a chance to rig something up to check the airflow pressure at the oil filler hole. Please note that I checked the airflow pressure not the volume. What I did was I modified an old filler cap by welding a tube on it and put it on the engine after it had reached operating temp. I then ran a hose from the modified cap to a pressure gage. At idle (900 RPM) the gauge read +2psi. As I increased the RPM the pressure dropped to just under 1/2 psi at 2000 RPM and to 0 psi by 2500psi with no movement from 2500 RPM to redline. The 2.0L has a OGTS Combination cam with hydraulic lifters, Weber carb, ported intake manifold and a Sprint exhaust manifold. I plan on checking my completely stock high milage 1.9L engine in the near future.
hth
Brian

My thoughts is this: No whale blow, problem! Oil blowing out the top, problem! Whale blow (no water ), good thing. I haven't opened my old block yet to check sequence, but you will have times when more air is "pushed" into the crankcase and more is "pulled" into the combustion chambers via the PVC setup. That's what makes the little "puff-puff". Stepping on the gas, naturally, causes less pressure due to the vac requirements of a hungry engine. opeldean, if you aign't smoking out the pipe or leaking on the ground, you are in good shape. And that's my 2c's .

The pressure was getting to me!!

I have been looking for this thread since I bought my GT in August 2006:banghead:. My engine was allegedly rebuilt by a PO 6-7 years ago and has less than 300 miles on the rebuild.

There is a fairly loud ticking sound that follows the engine speed and it has a strong gust blowing out the oil fill hole at idle as described in this thread. I found that the vacuum line to the PCV had been removed and capped off at both holes. I replaced the PCV orifice and ran a new vacuum line to the valve cover - but it made no noticable impact.

A compression test reveals all four cylinders are 160 psi +/- 5 dry.

I am going to assume that the crankcase pressure is normal and unrelated to the ticking unless someone tells me differently.

I'm gonna guess your ticking noise is a loose rocker arm pivot nut. Do a search and look for adjusting the valves. It's pretty straight forward. All you really need to check out is if your have solid or hydraulic lifters. HTH.

If you have the valve cover off look if there are any marks that show that the vlave cover is being touched by the valvespring retainer.
I once had a 2.2 injection valve cover and the middle boltholes broke off and were welded back on when I put it on the engine it made a tikking noise had to take away some of the weld.

For anyone having oil blowing out of the fill cap or other locations: I don't have GT's and the cast valve covers, but have Mantas/Asconas with the steel covers. On those cars and valve covers, there is a large line going into the valve cover from the air cleaner for drawing air INTO the crankcase, and a smaller line from the valve cover to the intake manifold, to a small protruding pipe on the intake manifold that has a small restriction in it. This whole system is the PCV system (positive crankcase ventilation) system and should, on average, put a low level of vacuum in the crankcase and draw blowby into the intake tract to be burned. This should work at idle and mild cruise conditions. I see all sorts of Opels with that small line from the valve cover plugged, and consequently with oil blowing out at various points. Also, this restriction shoudl be cleaned every now and then; they can get plugged.

Two years later

I mentioned the "windy" oil fill hole 2 years ago on an engine with lapped rings and poor compression. Well, I've rebuilt the engine and it runs dandy -- and I still have a mighty wind blowing out of this hole. The good news it that there is no oil blowing with it. I gather that the effect is normal, though I can't say I've noticed it with other cars.